(1) Field of the Invention
The invention is related to a rotary wing aircraft with a fuselage that comprises a framework structure having at least one hollow frame.
(2) Description of Related Art
A fuselage of an aircraft, and in particular of a rotorcraft, can at least partly be provided with a framework structure having one or more hollow frames in order to reduce an overall weight of the fuselage. Usually, such hollow frames consist of a plurality of hollow frame beams that are separately manufactured and subsequently assembled to define the framework structure. To this end, these separate hollow frame beams are interconnected during assembly at corresponding intersection points by means of suitable joints.
Such a fuselage is generally adapted to accommodate a basic ventilation system and an environmental control system, and can further be adapted to accommodate an air conditioning system. All these systems together have constituent parts and/or components that produce a flow of air at a specific spot in or on the aircraft, which is usually not the spot where the air should be expelled to cool or heat a certain region of the aircraft, such as its cockpit, or a selected component, such as a main window in the cockpit, or a person, such as the pilot of the aircraft. For instance, the document U.S. Pat. No. 5,037,041 describes a cockpit for a helicopter.
The aircraft ventilation and/or air conditioning systems generally consist of air generating components, which generate an air stream, e.g. pumps, fans and/or compressors, and of air ducts, which are implemented into the aircraft and, at least partly, accommodated in its fuselage in order to direct the generated air stream to a given region where it is expelled. The air ducts are realized by means of flexible hoses, tubes and/or pipes that are mounted to the fuselage and, thus, integrated into the aircraft volume.
However, such flexible hoses, tubes and/or pipes require a certain installation space that must be allocated and reserved in the aircraft. This installation space cannot be used for other purposes and, thus, further reduces an already limited available space in the aircraft.
The document US2010/0087131 describes an aircraft with air ducts that are at least partly implemented by means of dedicated tubes. These dedicated tubes are used to define air guide elements for connecting the air ducts that are bounded between overhead luggage compartment housing back walls and personal service ducts to a line system of an aircraft air conditioning system.
This aircraft air conditioning system, however, requires a comparatively large number of interconnected components. Accordingly, assembly of the aircraft air conditioning system is time-consuming and, therefore, expensive. Furthermore, due to the comparatively large number of interconnected components, this aircraft air conditioning system is prone to air leakage, leading to a reduced overall performance of the system.
The document US2012/0248244 describes a fuselage of an aircraft that is formed by load-bearing hollow structural elements, which are defined by longitudinal and transverse frames, as well as transverse beams. These longitudinal frames, transverse frames and transverse beams are interconnected at associated intersecting points to build up a lattice structure that is covered by an outer skin, thereby defining the shape of the fuselage. Furthermore, air ducts are integrated into the interconnected longitudinal frames, transverse frames and transverse beams and adapted to transport air for air conditioning purposes from an air conditioning system into a passenger compartment of the aircraft. Each such air duct is provided with one or more variable control valves for controlling respective flow cross sections of the air ducts, i.e. for controlling respective air flows and/or air pressures in the air ducts. Moreover, actuators such as pivoting flaps for controlling how an air stream is to be carried are provided in one or more of the intersecting points.
This lattice structure advantageously allows implementing an air conditioning system in a fuselage of an aircraft without requiring use of the above described flexible hoses, tubes and/or pipes. Thus, the installation space that would normally be required for these flexible hoses, tubes and/or pipes can be saved for other purposes.
However, the intersecting points where the longitudinal frames, transverse frames and transverse beams are respectively interconnected are prone to air leakage, as they would normally not fit perfectly to each other due to underlying manufacturing tolerances. Accordingly, the generated air stream that moves e.g. from an air duct in a longitudinal frame via an intersecting point into a transversal frame or beam would potentially leak at the intersecting point, therefore limiting the overall achievable performance of the air conditioning system. Furthermore, this lattice structure is not suitable for implementing an air conditioning or ventilating system in a cockpit region of an aircraft, which is structurally a very complex region, where generally no interconnectable longitudinal and transversal frames and/or beams exist.
The documents WO2012152934, CA2740666, US2011/0253836 and U.S. Pat. No. 5,441,326 also describe aircrafts that are provided with air ducts for air conditioning and/or ventilation purposes. According to these documents, the air ducts are integrated into available components of the aircrafts, such as insulating skin panels, cargo-fire-suppression agent distribution systems and/or overhead luggage bin modules.
Such an integration of air ducts into available components or structures is also known from other vehicles than aircrafts. For instance, the document U.S. Pat. No. 6,296,296 describes a door trim panel of a truck that is provided with an air duct of an associated air conditioning and/or ventilating system. The document U.S. Pat. No. 8,376,444 describes insert-molded structural air duct assemblies for cars.
The document EP1510454 describes a mobile platform interior panel having integrated ducts and insulation. The interior panel includes a body formed by an injection molding process, at least one duct integrated with the body and at least one layer of insulation also integrated with the body. The panel is formed using a low pressure forming process, such as reaction injection molding (RIM). The low pressure forming process allows the duct and insulation to be integrated with the body simultaneously with forming the panel from a material having desired insulating properties. The ducts are round in cross-section, have a substantially consistent cross-sectional area, and are straight along their length.
Other documents are to be considered: EP2452872, GB487023, U.S. Pat. No. 4,111,106, U.S. Pat. No. 5,037,041, U.S. Pat. No. 5,441,326, US2010/148003 and WO2012101439.
However, all of the above described air duct systems are more or less prone to air leakage. Furthermore, they are not suitable for implementing an air conditioning or ventilating system in an aircraft with reduced installation space requirements permitting its installation e.g. in a cockpit region of the aircraft, which inherently exhibits only limited available space